[LEAPSECS] Historican timezones (Was: Re: Looking-glass, through)

Paul Sheer p at 2038bug.com
Wed Jan 12 17:41:07 EST 2011

The Olson time library has all historican timezone information.

You can choose a zone, a time (back to the 1800's) and deduce
the precise zone offset in minutes and seconds.

This is inclusive of wierd time zones that were based on the hour
since sunrise (or some similar wierd thing), as well as more basic
things like daylight savings that were tried one year, and revoked
the following year by that countries government.

There are 3064 rules in the Olson time library zone files and 434
time zones, as well as GPS information for each zone.

It would seem a number of maintainers do track time zone
announcements from all over the world and keep these
rules up to date. The most recent update was November 2010.

Further, people updating the zone rules usually provide references
for the rule change, citing a government announcement.


On Wed, 2011-01-12 at 20:48 +0000, Clive D.W. Feather wrote:

> Rob Seaman said:

> > For instance, what authority will historians or lawyers consult to learn the applicable timezone offsets that were in force in some location(s) during some epoch(s) in question?


> <FX: falls about laughing>


> Those of us on the timezone list can't even find out this information for

> this year for many places. It's almost impossible to determine it for (say)

> 200 years ago for almost anywhere.


> This is *nothing* to do with what the underlying time scale is. Tony has it

> right: you have things completely backwards.


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